The prior art is replete with digital data communication systems that convey data between system sections or system components. Some data communication systems, such as optical transport networks (OTNs), transmit frame delineated serial streams of digital data, while other systems may transmit format-independent data streams. Conventional SONET/SDH networks transport data frames formatted in accordance with internationally standardized protocols. Generally, a data frame includes a relatively small number of bytes devoted to system overhead, a relatively small number of bytes devoted to forward error correction (FEC), and a relatively large number of bytes reserved for the actual client data payload. One specific data frame format utilized by OTNs is set forth in ITU-T Recommendation G.709/Y.1331 (International Telecommunication Union, February 2001). This data frame format is informally referred to as the “digital wrapper” format.
In a conventional digital wrapper frame, the FEC parity bytes cover the client data payload and the Operations, Administration, and Management (OA&M) overhead (including frame delineation) bytes. The standard digital wrapper frame structure utilizes all of the bytes allocated for FEC (1,024 bytes), regardless of the coding gain (error correction capability) actually required to correct for channel errors encountered within a given section of the data communication line. Consequently, prior art digital wrapper frames have no provision for an in-band data channel that receives FEC coverage.